Cellulosic structure and method for producing same



Patented Aug. 24, 1943 UNITED STATES PATENT OFFICE CELLULOSIC STRUCTURE METHOD FOR PRODUCING SAME Theron G. Finzel, Kenmore, N. Y., assignor to E.

I. du Pont de Nemours & Company, Wilming ton, DeL, a corporation of Delaware No Drawing. Application November 13, 1939,

Serial No. 304,216

11 Claims. (Cl. 8132) For purposes of definition, high tenacity signifies a strength of above 2 grams per denier,

low denier per filament signifies a denier per filament of less than 1, and "low thread denier" signifies a thread denier of less than 50.

When cellulose derivative yarn or thread spun by the conventional dry spinning process, the product possesse a low tenacity; e. g., only about 1.4 to 1.7 grams per denier. Also, it is im possible to spin, uninterruptedly or commercially, cellulose derivative yarn with filaments of extremely low denier, for instance materially below 1 denier per filament. Improvement in tenacity to 2.0, 2.5, 3.0 or more grams per denier opens entirel new fields of uses for cellulose derivative yarn. The ability to obtain yarn with filament denier as low as 0.5 and under results in the production of yarn and fabric of extreme softness and yarn of high knot strength.

Numerous yarn stretchin processes have been disclosed heretofore, but these prior art processes have only a limited commercial value because of certain, inherent, undesirable characteristics; e. g., too low a rate or degree of stretching of the yarn, the use of toxic materials in the stretching medium, the production of yarn in which the filaments adhere to each other thereby imparting harshness to the yarn, and the production of yarn which is of inferior quality.

It has now been found that filaments, yarn, thread or the like possessing tenacities of 2.5, 3.0 and even 4.0 grams per denier and more can be produced with thread or yarn deniers or low as 10 and with filament deniers as low as 0.15. Furthermore, yarn speeds of over 1,000 inches per minute can easily be obtained.

Thi invention has as an object a novel method of producing filaments, yarn, thread and the like comprising a collulose derivative, particularly organic acid esters of cellulose such as cellulose acetate.

A further object comprises improvements in the production of cellulose derivative filaments, yarn, thread and the like having a high tenacity and low denier, and having a pleasing softness and hand.

Other objects of the invention will appear hereinafter.

The objects of the invention are accomplished,

, in general, by treating yarn comprising a cellulose derivative, such as cellulose acetate, with a nitroparafiin which swells the yarn, then stretching the yarn while swollen, and thereafter removing the swelling agent while the yarn is maintained under tension.

The following examples illustrate preferred modes of applying the principles of the invention.

Example I A 300-d'cm'er, IOU-filament cellulose acetate yarn with a twist of 3 turns per inch and a tenacity of 1.5 grams 'per denier was passed into a bath consisting of 27.5% nitromethane and 72.5% toluol by weight, at the rate of 103 inches per minute, and drawn from the bath at the rate of 510 inches per minute. The length of yarn travel in the bath was 32.5 inches and the temperature of the nitromethane-toluol solution was held at 62 C. As the stretched yarn emerged from the bath, it was allowed to dry under a tension not exceeding 10 grams and wound on a suitable support. When tested, the driedyarn showed a tenacity of 4.3 grams per denier, was soft, and semi-lustrous. The filaments of the yarn were free and did not adhere to each other.

Example II A 200-denier, fi l-filament cellulose acetate yarn, having a twist of 3 turns per inch and a tenacity of about 1.5 grams per denier, was passed into a' bath consisting of 33.7% nitromethane and- 66.3% toluol by weight, at the rate of 6 inches per minute, and drawn from the bath at the rate of inches per minute. ,The length of yarn travel in the bath was 32.5 inches. The temperature of the nitromethane-toluol solution was held at 23.5 C. After emerging from the bath,

the yarn was handled as described in Example I. The stretched yarn showed a tenacity of 2.7 grams. per denier, was soft and somewhat de-= lustered. The filaments of the yarn were in free condition and were not stuck to each other.

Example III Untwisted, 580-denier cellulose acetate yarn containing 58 filaments and possessing a tenacity of 1.3 grams per-denier,-was passed into a bath consisting of 32.5% nitromethane and 67.5%

toluol at the rate of 208 inches per minute, and drawn from the bath at the rate of 1,080 inches per minute. The temperature of the solution was 47 C. The length of bath travel was 32.5 inches. The stretched yarn, after emerging from the bath, was handled in the manner described in Example I. The stretched yarn showed a tenacity of 4.0 grams per denier, was soft, and was somewhat delustered. The filaments of the yarn were in a free condition and did not adhere to each other.

Example IV A 200-denier cellulose acetate yarn having a twist of 3 turns per inch and containing 64 filaments, was passed into a bath consisting of 34.5% nitromethane and 65.5% toluol at the rate of 6 inches per minute and was drawn from the bath at the rate of 39 inches per minute. The temperature of the solution was 21 C. The length of bath travel was 32.5 inches. After withdraw:- ing from the stretching bath, the yarn was handled as described in Example I. The stretched yarn showed a tenacity of 3.9 grams per denier, was soft and glossy. The filaments of the stretched yarn did not adhere to each other.

Example V A 240-denier, 24-fllament cellulose acetate yarn having a twist of 3 turns per inch and possessing a tenacity of approximately 1.5 grams per denier was passed into a bath consisting of27.5% nitromethane and 72.5% toluol at the rate of 77 inches per minute, and was withdrawn from the stretching bath at the rate of 220 inches per minute. The length of bath travel was 32.5 inches and the temperature of the solution was held at 56 C. The method of treatiientafter removing from the stretching bath was similar to that de- 4 scribed in Example I. The stretched yarn showed a tenacity of 3.0 grams per denier, was soft and glossy. The individual filaments of the yarn were in a free condition and were not stuck to each other.

maple v1 Cellulose acetate yarn having a denier of 200 and a twist of 3 turns per inch, containing 64 filaments, and possessing a tenacity of about 1.5 grams per denier, was soaked in a solution consisting of 34% nitromethane and 66% toluol for one minnte. The temperature of the solution was held at 22 C. The length of the original yarn was one inch and was stretched to 13 inches In length in approximately one minute. The

stretched yarn was air dried under slight tension.

The dried yarn showed a tenacity of 4.5 grams per denier and was slightly delustered. The yarn was soft and the filaments of the yarn were in a free condition and not stuck to each other.

Example VII A 200-denier, 64-filament cellulose acetate yarn' having 3 turns per inch twist and a tenacity of 1.5 grams per denier was soaked for approximately one minute in a solution' consisting of 7% nitromethane and 93% carbon tetrachloride by weight. The temperature of the solution was held at 22 C. The length of the yarn immersed was 3 inches and it was stretched to 14 inches during a period of approximately one minute. After stretching, the thread was washed with carbon tetrachloride under tension and dried. The tenacity of the stretched yarn was 2.6 grams per denier. The thread was slightly delustered and the filaments in the thread were superminute.

ficially stuck to each other, but could be easily separated by passing under a slight tension over a guide at an acute angle.

Example VIII A 240-denier, 24-filament cellulose acetate yarn having a twist of 3 turns per inch and possessing a tenacity of approximately 1.5 grams per denier was passed into a solution containing 11.7% nitromethane and 88.3% trichlorethylene by weight, at the rate of 55 inches per minute, and withdrawn from the bath at the rate of 275 inches per-minute. The temperature of the solution during stretching was 38 C. to 40 C., and the length of bath travel was 32.5 inches. The stretched yarn was handled as described in Example I. The stretched yarn was soft and glossy and showed a tenacity of 3.5 grams per denier. The filaments of the yarn were in a free condition and did not adhere to each other.

Example IX A 240-denier, 24-filament cellulose acetate yarn having a twist of 3 turns per inch and showing a tenacity of approximately 1.5 grams per denier was passed into a bath consisting of 10.5% nitromethane and 89.1% isobutylalcohol by weight at the rate of inches per minute and was withdrawn from the bath at the rate 01' 275 inches per minute. The solution was heated to 62-65 0., and the length of bath travel was 32.5 inches. The stretched yarn was handled as described in Example I. The stretched yarn showed a tenacity of 2.2 grams per denier and the yarn was soft and glossy. The filaments were free and not stucl; to each other.

Example X A cellulose acetate yam having a denier of 240 and a twist of 3 turns per inch, and containing 24 filaments and showing a tenacity of approximately 1.5 grams per denier was passed into a bath consisting of 55% nitroethane and 45% toluol by weight, at the rate of inches per The rate of withdrawal from the bath was 550 inches per minute and the temperature 01. the bath during stretching was held at 43 C. The length oi! bath travel was 32.5 inches. After withdrawing the stretched yarn from the bath it was handledin the manner described in Example I. The stretched yarn showed a tenacity of 2.3 grams per denier, and was soft and glossy. The individual filaments were in a free condition and were not stuck to each other.

Example XI Cellulose acetate yarn was stretched under conditions similar to those described in Example X, with the exception that a solution consisting of- 63.5% nitropropane and 36.5% toluol by weight, held 'at a temperature of 74 C., was used.

The resulting yarn was soft and glossy and.

showed a tenacityof approximately 2.0 grams per denier.

Example XII A 240-denier, 24-filament cellulose acetate yarn having a twist of 3 turns per inch was passed into a bath consisting-o1 6% nitromethane and 94% water by weight, at the rate 01' 55 inches perminute. The rate or withdrawal was inches per minute, and the bath was held at a temperature 01' 55 C. The length or bath travel was 32.5 inches. The resulting yarn was sort,

l h ly d lustered. hbwins a tenacity of 2.7 grams per denier. The filaments or the yarn were in a free condition and were not'stuck to each other.

Although the above examples are directed to the treatment of cellulose acetate filaments, thread, and yarn, it is to be understood that the invention may likewise-be applied to filaments, thread, yarn and the like comprising other organic acid, simple or mixedre'sters of cellulose; e. g., cellulose nitrate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate, cellulose butyrate. It may also be applied to cellulose ethers; e. g., methyl cellulose, ethyl cellulose, glycol cellulose, and other cellulose derivatives, provided that the cellulose derivative to be treated is swelled by,the nitroparafiin, and provided that the restrainingagent, if any is used, has substantially no swelling action on the cellulose derivativ structure treated.

Instead of nitromethane, one may use nitroethane, nitropropane, or other nitroparaflfin, whether straight chain or branched chain, which is capable of severely swelling the cellulose derivative structure. Best results are obtained with a nitroparafiin containing no more than six carbon atoms, which paraffin group' is also saturated. With the increase in the molecular weight of the nitroparaffin, in a homologous series, the swelling effect decreases with the result that less and less restraining material or diluent is necessary. When nitromethane is used with toluol as the restraining material, the best results are obtained with 20% to 40% by weight of nitromethane and 80% to 60% by weight of toluol;

- similar limits in the case of the higher nitroparafiins are nitroethane 35% to 70%, toluol 65% to 30%, and l-nitropropane 50% to 100%, toluol 50% to 0% by weight.

The bath in which the yarns are stretched have a swelling or softening efiect on the yarns. but the swelling or softening effect must be restrained to proceed only to such an extent that stretching of the yarns can be carried out without causing excessive weakening. If the swelling agent in the bath is too active in itself, some restraining agent which is miscible with the swelling agent and is substantially inert toward the cellulose derivative is preferably added to decrease the swelling effect. For instance, nitromethane swells and even dissolves cellulose ace tate under certain condition and cannot, therecase of water, the limits appear to be 92% to 97% water, along with 8% to 3% nitromethane.

As a rule, the lower the concentration of any one active swelling agent, the higher must be the temperature to give good stretching condiis too low, the stretching tension will rise excessively and the thread will break. If, on the other hand, the swelling activity of the solution is too high because of too high an operating temperature or too high a concentration of the active swelling agent, the filaments may then stick to each other, or in the extreme. case, the thread will become excessively weak in the swollen condition, and finally break.

After immersion in the swelling bath, it is preferable to stretch the thread as soon as it will yield to stretching, rather than allow the thread topre-swell, followed by stretching.

Luster of the stretched yarn can be controlled by increasing or decreasing the swelling activity of the bath within the operating range of temperature and concentration of a swelling agent. The lower the swelling activity of the bath, the less the lust'er the stretched and dried'yarn will exhibit; and the higher the swelling activity, the higher the luster.

The filaments, yarn, thread and the like to be treated in accordance with this invention may be twisted or may have no twist, but it is preferably given a slight twistprior to treatment.

The stretch ratio is at least 2, but may be 5,

10, 20 or more, although the stretch ratio is preferably from 5 to 15.

The rate at which the swelling yarn is'stretched swelling yarn may be from 2 to 35 or more inches fore, be used in 100% concentration. If, however, toluol is added, the swelling eflect of the nitromethane is decreased and a concentration In place of toluol, other restraining agents such as benzol, xylol, naphtha, isopropyl ether, ethyl alcohoL'methyl alcohol, isobutyl alcohol, carbon per minute for each inch of bath length through which the yarn is-drawn. .I'he stretched yarn is taken from the swelling bath immediately after stretching is completed and the bath adhering to tetrachloride, trichlorethylene, ethylene dichloride, orwater may be used.

The actual ratio of restraining agents to swelling agents will depend upon the specific character of each. For instance, when isobutyl alcohol is used as a restraining agent along with nitromethane as the swelling agent, between 80% and 92% of the alcohol should be used to get the best results, while 20% to 8% of nitromethane will give a sufficient swelling eflect. Inthe the stretched yarn is removed by allowing the bath to evaporate from the yarn, or washing the yarn with a suitable material which will not substantially swell or otherwise adversely affect the yarn, but will remove the bath residuum there'- from. If the yarn is washed to remove the stretching medium, the washing agent must be eliminated, for instance, by drying.

After the tenacity of the cellulose derivative yarn has been increa ed by the above-described method,.the derivative may be regenerated by known processes into cellulose, such as, for instance, by treating with alcoholic caustic under tension- If this regenerating step is properly carried out, the improved tenacity of the yarn is not lost, but generally is not only retained but increased.

In addition to filaments and yarn, it is to be understood that the principles of the invention can also be applied to ribbons or other structures of cellulose derivatives.

The yarn produced by the herein described process shows a very definite improvement intenacity over unstretched yarn or similar chemical cimposition. An improvement in softness of C r I I l 'I 1 a extremely fine filament demers can be produced. Another advantage is the improved knot strength of the stretched Yam. 7

Since it is obvious that many changes an modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited except as set forth in the appended claims.

I claim:

1. The process which comprises swelling a. cellulose organic derivative structure with a nitroparaifin, containing not more than six carbon atoms, and stretching the swollen structure.

2. The process which comprises swelling a cellulose organic derivative structure with a nitroparafiin containing not more than six carbon atoms, stretching the swollen structure, and then removing the nitroparafiin from the structure while holding the structure under tension.

3. The process which comprises swelling cellulose organic derivative filaments, yarn, thread and the like with a nitroparaifin containing not more than, six carbon atoms, stretching the swollen filaments, yarn, thread and the like, then removing the'nitroparafiin from the filaments, yarn, thread and the like while holding the latter under tension.

4. The process which comprises swelling cel-, lulose organic acid ester filaments, yarn, thread and the like with a nitroparafiin containing not more than six carbon atoms, stretching the swollen filaments, yarn, thread and the like, then removing the nitroparaifinjrom the filaments,

and the like with nitromethane and an agent for restraining the swelling effect oi the nitromethand the like, then removing the nltromethane from the filaments, yarn, thread and the like while holding the latter under tension.

7. The process which comprises swelling cel-- the swollen filaments, yarn, thread and th like yarn, thread and the like while holding the latter the like while holding the latter under tension.

6. The process which comprises swelling cellulose organic acid ester filaments, yarn, thread then removing the nitroparafiin from the filaments, yarn, thread and the like while holding the latter under tension. ,9. The process which comprises swelling acetone-soluble cellulose acetate filaments, yarn, thread and the like with a nitroparafiin containing not more than six carbon atoms and an agent for restraining the swelling effect of the nitroparaflin liquid, stretching the swollen filaments, yarn, thread and the like, then removing the nitroparaffin from the filaments, yarn, thread and the like while holding the latter under tension.

10. 'Ihe process which comprises swelling acetone-soluble cellulose acetate filaments, yarn, thread and the like with nitromethane, and an agent for restraining the swelling eifect of the nitromethane, stretching the swollen filaments, yarn, thread and the like, then removing the nitromethane from the filaments, yarn, thread and the like while holding the latter under tension.

11. The process which comprises swelling acetone-soluble cellulose acetate filaments, yarn, thread and the like with a composition consisting of from about 20% to about 40% by weight; of nitromethane and from about 80% to about of toluol, stretching the swollen filaments, yarn, thread and the like, then removing the nitroparaflin from the filaments, yarn, thread and the like while holding the latter under tension.

THERON G. FINZEL. 

